Sudden stoppage of liquid flow causes pressure surges in piping systems. These surges occur because shutting the flow of liquid sends an abrupt pressure wave back up the line towards the flow source. This pressure wave creates a phenomenon known as “water hammer” that shocks pipes and creates a hammer-like noise. The water hammer phenomenon can be intense enough to break pipe supports or even rupture pipes. The water hammer phenomenon is not limited to pipes carrying water, and also occurs with other types of liquids, for example, in association with fill valves dispensing jet fuel. For example, fast closure of a fill valve in an aircraft fuel tank can result in a surge pressure wave of 600 to 1,000 psig (4134 to 6890 kPa) being generated at the valve closure point and traveling upstream into inlet piping at a rate of approximately 2800 feet/second (853.44 meters/second).
One known method for reducing water hammer is to provide surge relief valves installed upstream of a fill valve or as a separate surge relief valve attached to the fill valve itself to relieve the surge. Ideally, the separate relief valve is installed on the fill valve itself, at the actual location of the surge pressure wave generation. However, the fill valve must be able to accommodate the separate surge relief valve attachment, and there must be space for the attachment at the fill valve location. If the fill valve does not incorporate a relief valve, the surge relief valve may be located on the inlet pipe as close to the fill valve as possible, but such location may be limited by interference from surrounding pipes or structure.